Where
is the New Jerusalem during the millennial period? I believe it will
be above the earth during the thousand years and not come down to rest
until after the earth has been recreated.

Revelations 21:

1Now I saw a new heaven and a new earth, for the first heaven and the first earth had passed away. Also there was no more sea. 2Then I, John,[a] saw the holy city, New Jerusalem, coming down out of heaven from God, prepared as a bride adorned for her husband. 3 And I heard a loud voice from heaven saying, “Behold, the tabernacle of God is with men, and He will dwell with them, and they shall be His people. God Himself will be with them and be their God. 4
And God will wipe away every tear from their eyes; there shall be no
more death, nor sorrow, nor crying. There shall be no more pain, for the
former things have passed away.”

I once did a drawing of the New Jerusalem and the earth to scale.
The New Jerusalem was just too big to fit on this little planet the size
it is now. I seem to recall that if Israel's borders in the future
millennial period only stretch from the Euphrates to the Nile, then the
New Jerusalem is too big. When I placed the New Jerusalem on the
surface of the earth, it didn't work. The curvature of this small
planet made the curvature of the base of the New Jerusalem longer than
the 1,500 miles that the Bible said it should be. Furthermore, the
troposphere of the present earth only extends 9 miles. Presumably there
wouldn't be any air above the first few floors. In addition, gravity
at the higher levels would be minimal. Finally, the earth's crust is
just not thick enough to bear the weight of such a colossal city.
Bearing all these things in mind, I believe the New Jerusalem will hang
over earth like the moon (perhaps in synchronous orbit above the earthly
Jerusalem). When the earth is recreated after the millennium, it
appears to me that it will be a much larger planet and be able to
support the New Jerusalem. The sky might just go on and on.